MTB Brake Bubble Bleed – BikeCo Tips & Tricks

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mountain bike bubble bleed brake

MTB Brake Bubble Bleed – BikeCo Tips & Tricks

This BikeCo Tips & Tricks video illustrates how a MTB Brake Bubble Bleed works.

Assuming a quality initial bleed most lever related issues can be traced back to air in the master cylinder. An occasional bubble bleed will help keep your lever feel consistent and brake performance at its best.

OK, disclaimer time. Brakes are critical to your safety. If you aren’t sure of your brakes walk it back and take it to a professional. You do you – we’re just showing you some ideas to add to your mental tool kit…

MTB Brake Bubble Bleed

Ensure you have the correct brake fluid as spec’d by the manufacturer. Never mix fluid types or brands.

Arrange the brake so the bleed port is at the highest point in the system.

Open the bleed port.

In this video we use a craft bottle. Shimano’s small “bucket” is another popular method. In a pinch you can use a syringe, however it is more difficult to control the amount of pressure exerted on the bladder.

Gently squeeze the craft bottle. You aren’t trying to push fluid into the system as much as DRAW the bubbles out with a slight vacuum pressure.

You will typically see the bubble enter the bottle. Pulling the lever in and out as well as shaking the brake line may help free hard to extract air bubbles.

Replace the bleed port and clean fluid from the master cylinder and lever.

Ensure proper brake performance. If the lever feel has not improved you can repeat the procedure. If lever feel still does not improve seek a professional.

Test ride the bike and check power as well as lever feel.


NOTE: This procedure will “top off” your brake lever as your pads wear. It is critical to open the bleed port to move the pistons or install new pads. If you do not open the bleed port and force the pistons into the caliper you risk over pressurizing the brake bladder which may cause failure.


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